They are childhood friends and she gave him a smug face. In the context of this manga, it's like starting to discuss your wedding day after 10 years of dating and living together.Wow another childhood friends again!?
Maybe the real childhood friend is the girlfriend we dated along the way.starting to think this author has a thing for childhood friends
I think this story takes place in the mirror universe where childhood friends always win. Just give him time.Childhood Friend Losing Curse : « It’s not just for Girls. »
Source?